Abstract

The primary purpose of this work was to identify the process by which the control of variables' strategy develops.

Investigations are described which indicate that the strategies used on 'control of variables' tasks are task specific. The quasi/empirical nature of science tasks is shown to affect the use of the control strategy.

Further investigations are described that indicate the existence of a concrete operational control strategy which has as its basis negation by elimination and cancellation, and not Piaget's formal level operation of negation by neutralisation.

Two major studies, one at the Secondary School and one at the Junior School level, are described in which four parallel substages in the development of the control strategy were noted. At the concrete operational level these substages represented an increasing ability to produce a consistency between judgments and experimental results through the formation of increasingly sophisticated strategies, i.e. through attendance to first order relations. At the formal operational level the substages represented an increasing ability to compare criteria for the use of strategies, i.e. attendance to second order relations.

Neo-Piagetian procedures are applied and the calculation of the M demand for the substages tends to confirm a static model for the size of M space.